Support new WhatsApp database schema

https://github.com/KnugiHK/Whatsapp-Chat-Exporter/issues/9

Whatsapp_Chat_Exporter/data_model.py

@@ -0,0 +1,35 @@
+from datetime import datetime
+from typing import Union
+
+
+class ChatStore():
+    def __init__(self, name=None):
+        if name is not None and not isinstance(name, str):
+            raise TypeError("Name must be a string or None")
+        self.name = name
+        self.messages = {}
+    
+    def add_message(self, id, message):
+        if not isinstance(message, Message):
+            raise TypeError("Chat must be a Chat object")
+        self.messages[id] = message
+
+    def delete_message(self, id):
+        if id in self.messages:
+            del self.messages[id]
+
+class Message():
+    def __init__(self, from_me: Union[bool,int], timestamp: int, time: str, key_id: int):
+        self.from_me = bool(from_me)
+        self.timestamp = timestamp / 1000 if timestamp > 9999999999 else timestamp
+        self.time = datetime.fromtimestamp(time/1000).strftime("%H:%M")
+        self.media = False
+        self.key_id = key_id
+        self.meta = False
+        self.data = None
+        self.sender = None
+        # Extra
+        self.reply = None
+        self.quoted_data = None
+        self.caption = None
+